One or more integrated circuits (“IC”) dice may be assembled into an IC package by physically and electrically coupling them to a substrate made of organic or ceramic material. One or more IC packages may be physically and electrically coupled to a printed circuit board (“PCB”) to form an “electronic assembly”. The “electronic assembly” may be part of an “electronic system”. An “electronic system” is broadly defined herein as any product comprising an “electronic assembly”. Examples of electronic systems include computers (e.g., server, router, desktop, laptop, hand-held, Web appliance, etc.), wireless communications devices (e.g., cellular phone, cordless phone, pager, etc.), computer-related peripherals (e.g., printer, scanner, monitor, etc.), entertainment devices (e.g., television, radio, stereo, tape and compact disc players, video cassette recorder, camcorder, game device, digital camera, MP3 (Motion Picture Experts Group, Audio Layer 3) player, etc.), and the like.
In the field of electronics there is competitive pressure among manufacturers to drive the performance of their equipment up while driving production costs down and maintaining acceptable yield and reliability. This is especially true for packaging of dice on substrates, where problems with flux overspray may reduce yield and/or increase throughput time.
One of the conventional methods for mounting an IC on a substrate is called “controlled collapse chip connect” (C4). In fabricating a C4 package, the electrically conductive terminations or lands (generally referred to as “electrical contacts”) of an IC component are soldered directly to corresponding lands on the surface of the substrate using reflowable solder bumps or balls. The C4 process is widely used because of its robustness and simplicity. In a known C4 process, a plurality of solder bumps or balls may be arranged in a pattern upon the substrate where an IC is to be mounted.
Flux may subsequently be deposited on the C4 bump region to help maintain the die or dice in place and to remove metal oxides that may otherwise prevent high quality metal bonding. One fluxing goal is to apply an even amount of flux to the bump field and to restrict the flux presence in other areas, such as areas outside the die-bonding area. These keep-out areas may include areas containing die-side lands, which lands may be used to mount additional components around the die or dice. Die-side lands may have been coated with solder, such as solder paste, prior to an application of flux spray. If excess flux extends onto die-side lands, the solder paste may be contaminated. This may lead to reduced yield and increased processing time.